Few major dam sites are investigated today without recourse to aerial photography. Not long ago aerial photos were used almost solely for the production of planimetric and topographic maps. In dam investigations these maps were used to determine storage capacities of reservoirs and estimate earthwork quantities. At present, however, specialists are concentrating on the analysis and interpretation of diagnostic details of the natural and cultural landscape recorded on aerial photos. Among the many studies requiring experienced specialists are the detection of unstable slopes, the discovery of various types of selected construction materials, prediction of foundation conditions, and the location of tentative earth and concrete structures to take advantage of favorable geologic conditions.